The present invention relates to a treatment method of a photoresist layer formed on a substrate surface by using a positive-working chemical-amplification photoresist composition for decreasing the surface defects in the patterned resist layer which can be detected by using a special inspection instrument.
Along with the trend in recent years in the field of semiconductor devices toward a higher and higher degree of integration, mass production of LSIs of a design rule 0.18 μm has already been industrialized and mass production of LSIs of the design rule 0.15 μm will shortly be on the start line.
While the process of photolithographic patterning of a photoresist layer on the substrate surface is undertaken in the manufacture of semiconductor devices, it is essential that the light for the patterning light exposure of the photoresist layer has a short wavelength in order to accomplish a high pattern resolution of the patterned resist layer. In this regard, the g-line light of 436 nm wavelength used in the early development stage of the photolithographic technology as the patterning exposure light was replaced with the i-line light of 365 nm wavelength which in turn has been replaced with the KrF excimer laser beams of 248 nm wavelength constituting the major current of the patterning exposure light in the modern photolithographic technology. Furthermore, ArF excimer laser beams of 193 nm wavelength are now expected to be the patterning exposure light of the coming generation and active development works are now under way for the photolithographic processes utilizing not only the KrF excimer laser beams but also the ArF excimer laser beams and photoresist materials suitable for use in the process utilizing these excimer laser beams.
As is well known, namely, the photoresist composition used as the major current in the early stage was the positive-working photoresist composition comprising a novolak resin as the resinous ingredient and a naphthoquinone diazidosulfonate ester compound as the photosensitive ingredient. Photoresist compositions of this type, however, could hardly comply with the technological requirements in the photolithographic patterning works using the KrF excimer laser beams or other light sources of further shorter wavelengths. This problem of the above mentioned photoresist compositions can be overcome by the use of so-called chemical-amplification photoresist compositions including the positive-working chemical-amplification ones, in which the alkali-solubility of the resinous ingredient in the light-exposed areas is increased by reacting with the acid generated from a radiation-sensitive acid-generating agent, and the negative-working chemical-amplification ones, in which the alkali-solubility of the resinous ingredient in the light-exposed areas is decreased by reacting with the acid generated from a radiation-sensitive acid-generating agent.
The requirements to be satisfied by the chemical-amplification photoresist compositions heretofore developed include high photosensitivity to the patterning exposure light, high pattern resolution and heat resistance of the patterned resist layer, focusing depth latitude, orthogonality of the cross sectional profile of the patterned resist layer and holding stability, i.e. the stability against degradation of the cross sectional profile of a patterned resist layer due to contamination with an amine compound and the like during standing between patternwise light exposure and post-exposure baking treatment of the resist layer as well as the substrate dependency which means adaptability of the photoresist composition to substrates having surface layers of different natures such as insulating materials, e.g., silicon nitride, semiconductor materials, e.g., polycrystalline silicon, and ceramic materials, e.g., titanium nitride. Namely, the cross sectional profile of the patterned resist layer is affected by the nature of the substrate surface on which the resist layer is formed.
In addition to the above mentioned various requirements, a recent technological issue relative to the performance of a chemical-amplification photoresist composition is the problem of surface defects which must be overcome in order to accomplish a high-quality patterned resist layer.
The above mentioned surface defect of a patterned resist layer is a disordered resist pattern such as infidelity of the resist pattern to the photomask pattern, deposition of scums or dust particles, short-circuiting between resist pattern lines and so on and is detectable by examining the patterned resist layer vertically from above with a special surface-defect detector (for example, Model KLA, manufactured by KLA Co.).
The yield of semiconductor devices is greatly decreased when the number of the above-mentioned surface defects is large and the semiconductor device cannot exhibit excellent performance even when the conventional requirements for the photoresist composition are satisfied. Thus, one of the important technological problems to be solved urgently in the manufacturing process of semiconductor devices is how to decrease the surface defects. Unless the problems of surface defects are solved, great difficulties would be encountered in the mass production of semiconductor devices.
The inventors previously could arrive at a success to reduce occurrence of such surface defects of patterned photoresist layers to some extent by modifying the formulation of the positive-working photoresist solutions. It is, however, a very desirable way in the photolithographic patterning technology if the problems of the surface defects could be solved effectively without such a modification of the formulation of the positive-working photoresist solutions.